As part of the ongoing objective of automotive manufacturers of producing quality automotive vehicles, every effort is made to ensure that new vehicles are quiet and essentially free of squeaks and rattles. Testing for such problems is particularly important upon new vehicle roll out when body parts and subassemblies are first assembled as a production vehicle.
Previously, one or more vehicles were shipped from the assembly line back to a stationary test facility during vehicle roll out where they were tested on a stationary four-poster hydraulic test setup through a series of vibration tests. The vehicle could also be tested in temperature cycles and in simulated sunlight. The results of the testing was communicated back to the assembly plant at the earliest within several days or a few weeks of the assembly line start-up. With two shift operation, this can mean that 1,000 cars per day may be produced with an annoying squeak or rattle that can, in some instances, be eliminated as a running change. Since it is much less expensive to eliminate problems during assembly than as a warranty repair post assembly, significant savings can be achieved if the time between manufacture and problem identification is reduced.
In addition to squeak and rattle problem detection, problems relating to temperature cycling and durability relating to sunlight exposure have generally been conducted at stationary test facilities or remote proving grounds to which cars are transported from the assembly plants.
Environmental test facilities are most useful during initial vehicle roll out because once the vehicle design and assembly techniques are finalized, most problems have been eliminated and there is a reduced need for ongoing testing. The cost of environmental test facilities including a fourposter suspension testing system is substantial and it is economically unfeasible to include a stationary test facility at each assembly plant.
Four-poster hydraulic test units require predetermined seismic masses to assure accurate and repeatable test results. Over 100,000 pound seismic masses are used to assure testing accuracy. In stationary test facilities, the four-poster is permanently mounted on a concrete base which forms the seismic mass.
Extensive computer simulations and simulations based upon actual drive profiles have been developed for use at the stationary test facilities so that almost any driving surface such as gravel roads, potholes, cobblestone roads, smooth roads with expansion joints, or the like can be simulated for various time periods. Such testing offers the advantage of allowing a vehicle to be tested for drivability, squeaks and rattles in various road conditions without actually driving the vehicle and subjecting it to wear and tear or otherwise being damaged in the course of driving.
These and other disadvantages and problems have been overcome and resolved by the present invention as summarized below.